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cfq: break apart merged cfqqs if they stop cooperating

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cfq_queues are merged if they are issuing requests within the mean seek
distance of one another.  This patch detects when the coopearting stops and
breaks the queues back up.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jeff Moyer 2009-10-23 17:14:52 -04:00 committed by Jens Axboe
parent b3b6d0408c
commit e6c5bc737a
1 changed files with 76 additions and 3 deletions
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79
block/cfq-iosched.c
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@ -38,6 +38,12 @@ static int cfq_slice_idle = HZ / 125;
*/
#define CFQ_MIN_TT (2)
/*
* Allow merged cfqqs to perform this amount of seeky I/O before
* deciding to break the queues up again.
*/
#define CFQQ_COOP_TOUT (HZ)
#define CFQ_SLICE_SCALE (5)
#define CFQ_HW_QUEUE_MIN (5)
@ -116,6 +122,7 @@ struct cfq_queue {
u64 seek_total;
sector_t seek_mean;
sector_t last_request_pos;
unsigned long seeky_start;
pid_t pid;
@ -1036,6 +1043,11 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
{
struct cfq_queue *cfqq;
if (!cfq_cfqq_sync(cur_cfqq))
return NULL;
if (CFQQ_SEEKY(cur_cfqq))
return NULL;
/*
* We should notice if some of the queues are cooperating, eg
* working closely on the same area of the disk. In that case,
@ -1050,6 +1062,8 @@ static struct cfq_queue *cfq_close_cooperator(struct cfq_data *cfqd,
*/
if (!cfq_cfqq_sync(cfqq))
return NULL;
if (CFQQ_SEEKY(cfqq))
return NULL;
return cfqq;
}
@ -1181,7 +1195,7 @@ static int cfqq_process_refs(struct cfq_queue *cfqq)
static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
{
int process_refs;
int process_refs, new_process_refs;
struct cfq_queue *__cfqq;
/* Avoid a circular list and skip interim queue merges */
@ -1199,8 +1213,17 @@ static void cfq_setup_merge(struct cfq_queue *cfqq, struct cfq_queue *new_cfqq)
if (process_refs == 0)
return;
cfqq->new_cfqq = new_cfqq;
atomic_add(process_refs, &new_cfqq->ref);
/*
* Merge in the direction of the lesser amount of work.
*/
new_process_refs = cfqq_process_refs(new_cfqq);
if (new_process_refs >= process_refs) {
cfqq->new_cfqq = new_cfqq;
atomic_add(process_refs, &new_cfqq->ref);
} else {
new_cfqq->new_cfqq = cfqq;
atomic_add(new_process_refs, &cfqq->ref);
}
}
/*
@ -2029,6 +2052,19 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_queue *cfqq,
total = cfqq->seek_total + (cfqq->seek_samples/2);
do_div(total, cfqq->seek_samples);
cfqq->seek_mean = (sector_t)total;
/*
* If this cfqq is shared between multiple processes, check to
* make sure that those processes are still issuing I/Os within
* the mean seek distance. If not, it may be time to break the
* queues apart again.
*/
if (cfq_cfqq_coop(cfqq)) {
if (CFQQ_SEEKY(cfqq) && !cfqq->seeky_start)
cfqq->seeky_start = jiffies;
else if (!CFQQ_SEEKY(cfqq))
cfqq->seeky_start = 0;
}
}
/*
@ -2391,6 +2427,32 @@ cfq_merge_cfqqs(struct cfq_data *cfqd, struct cfq_io_context *cic,
return cic_to_cfqq(cic, 1);
}
static int should_split_cfqq(struct cfq_queue *cfqq)
{
if (cfqq->seeky_start &&
time_after(jiffies, cfqq->seeky_start + CFQQ_COOP_TOUT))
return 1;
return 0;
}
/*
* Returns NULL if a new cfqq should be allocated, or the old cfqq if this
* was the last process referring to said cfqq.
*/
static struct cfq_queue *
split_cfqq(struct cfq_io_context *cic, struct cfq_queue *cfqq)
{
if (cfqq_process_refs(cfqq) == 1) {
cfqq->seeky_start = 0;
cfqq->pid = current->pid;
cfq_clear_cfqq_coop(cfqq);
return cfqq;
}
cic_set_cfqq(cic, NULL, 1);
cfq_put_queue(cfqq);
return NULL;
}
/*
* Allocate cfq data structures associated with this request.
*/
@ -2413,11 +2475,22 @@ cfq_set_request(struct request_queue *q, struct request *rq, gfp_t gfp_mask)
if (!cic)
goto queue_fail;
new_queue:
cfqq = cic_to_cfqq(cic, is_sync);
if (!cfqq || cfqq == &cfqd->oom_cfqq) {
cfqq = cfq_get_queue(cfqd, is_sync, cic->ioc, gfp_mask);
cic_set_cfqq(cic, cfqq, is_sync);
} else {
/*
* If the queue was seeky for too long, break it apart.
*/
if (cfq_cfqq_coop(cfqq) && should_split_cfqq(cfqq)) {
cfq_log_cfqq(cfqd, cfqq, "breaking apart cfqq");
cfqq = split_cfqq(cic, cfqq);
if (!cfqq)
goto new_queue;
}
/*
* Check to see if this queue is scheduled to merge with
* another, closely cooperating queue. The merging of